This invention relates generally to electronic tone controls, especially those for musical instruments, and in particular describes a novel tone control providing a great range of control with a single knob.
Many tone controls have two knobs, one for controlling the level of bass or low frequencies, the other for treble or high frequencies. Other types have three knobs: two for the functions described above and a third for the middle range of frequencies.
More economical, simple controls provide only a single control knob which typically serves only as an attenuator for high frequencies. In certain multichannel audio devices, for example, multichanneled stringed musical instruments as described in U.S. patent application .pi.611048, filed Sept. 8, 1975, now U.S. Pat. No. 4,069,732 and assigned to the assignee of this application, it becomes desirable to exercise a great deal of tonal control over each channel as with multiknob tone controls. yet not to multiply the number of knobs necessary to the point of confusion. Accordingly, a primary object of the present invention is to provide a circuit which provides bass and treble boost, yet still provides the option for passing the input signal unaffected and to select between these options continuously with a single knob.
A further object of this invention is to provide radically different waveshapes for a square wave input, a fairly common waveform resulting from overdriving or clipping a sinusoidal waveform of the kind produced by stringed musical instruments. Briefly, these objects have been achieved by devising a circuit consisting of a differentiator, an integrator, and a potentiometer connected to their outputs and to the circuit input to control the frequency characteristic of the output signal.